Means for producing high vacuums.



' WITNESSES No. 852,947. PATENTED MAY 7, 1907.

. W.-GAEDE. MEANS FOR PRODUCING HIGH VAGUUMS.

APPLICATION FILED AUG. 17, 1906.

INVENTUF\ srrns ATENT @FFICE.

WOLFGANG GAEDE, OF FREIBURG, GERMANY.

MEANS FOR PRODUCING HIGH VACUUIVIS.

Specification of Letters Patent.

Patented May '7, 1907.

To all whom it may concern:

Be it known that I, WOLFGANG GAEDE, a subject of the German Emperor,residing at Freiburg i/Br., Salzstrasse l3,v Germany, have inventedcertain new and useful Improved Means for Producing High vacua; and I dohereby declare the following to be a full, clear, and exact descriptionof the invention, such as will enable others skilled in the art to whichit appertains to make and use the same.

The invention refers to apparatusfor producing a vacuum and moreespecially to that class of vacuum pumps in which a'drum con sisting ofa plurality of suitably shaped chambers is immersed in a liquid bath andby rotation withdraws gas or air from the vessel that is to be exhaustedand discharges said air either into the atmosphere or into a casingsurrounding the drum and being partially exhausted by means of anauxiiary pump or other exhausting means such as are generally known inthe art.

The invention consists in the hereinafter described special arrangementof the chambers constituting the rotating drum in this class of airpumpsby which the apparatus is enabled to produce a considerably highervacuum than was hitherto possible with similar devices.

In the accompanying drawing Figure 1 is a vertical section through thepump forming the subject of my invention, Fig. 2 is a cross section online 2-2 of Fig. 1, Figs. 3 and 4 are likewise cross sections showingmodifications and Fig. 5 is a perspective view of the completeapparatus.

In the drawing 1 is a stationary casing made of any suitable strong andgastight material, such as for instance cast iron. The casing 1 isprovided at the center of one of its flat sides with a stuliing box 2through which is introduced a shaft 3 carrying a pulley 4 or any othersuitable means for imparting rotation to the shaft. Fixed to the shaft 3is a drum 5 consisting of inner chambers 6 and an outer chamber 7. Theinner and outer chambers are in communication by means of holes oropenings 8 and 8 The outer chamber is also in communication with theinterior of the casing 1 by means of a central opening 9. Through thiscentral opening 9 a pipe 10 is introduced the inner end of which is bentupward. Thepipe 10 passes through a her-- metically sealed joint 11 inthe wall of the casing at a point just opposite the opening 9. At apoint near the top of the casing a stud 12 is likewise hermeticallyfixed into the wall of the casing.

In the example shown in Fig. 2 there are provided two inner chambers 6,designated y'the reference letters 6 and 6". They are separated fromeach other by radial walls and communicate with the interior of thecasing 1 by means of helical channels 13 and 13 respectively, and withthe outer chamber 7 by means of the abovementioned openings 8" and 8".At the center of the drum the radial walls, separating the singlechambers 6 from each other, are cut away so that a wide opening 14 isformed by means of which all the chambers 6 are in intercommunicationwith each other. v

For the purpose of operation the casing 1 is filled with liquid of anysuitable kind, preferably with mercury, up to a point slightly above themiddle, that is to say, to such a height that the stuffing box 2 and thecentral opening 9 of the drum 5 are well below the surface of theliquid. The stud 12 is connected to any ordinary airpump or ejectorcapable of producing a vacuum of about 20 millimeters of quicksilver andthe pipe 10 is put into communication with the vessel that is to beexhausted.

By means of the auxiliary pump, not shown in the drawing, the aircontained by the casing and the vessel to be exhausted is drawn oifuntil the maximum of the capability of the auxiliary pump, that is tosay, for instance, 20 millimeters of quicksilver, is reached. Then thedrum is rotated by means of the pulley 4 or by hand in the senseindicated by the arrows in Figs. 2 to 4. In the position shown in Fig. 21t will be seen that by means of the opening 8 the inner chamber 6 is incommunication with the outer chamber 7 and by means of the pipe 10 withthe vessel to be exhausted. Since the mercury in the drum tends tomaintain its level as the drum rotates in the sense of the arrow, a partof it will flow out into the helical channel 13 but the greater partwill pass through the opening 14 in the center of the drum into thechamber 6*. Thereby the free space within the chamber 6 will increaseand consequently the air contained in the vessel to be exhausted will bedrawn off and will fill the chamber 6*. At the same time the aircontained in the chamber 6 will be forced out into the channel 13 and assoon as the opening at the outer end of this chan nel emerges above thesurface of the liquid it will be in communication with the air 1n theinterior of the casing 1 and will be sucked off by the auxiliary pump.This process continues until the opening 8 is submerged, when the vesselto be exhausted will be altogether sealed for a short time, that isduring the period in which both openings 8 an 8 are submerged. Thenopening 8* will emerge and now the same play will be repeated, with thisexception that the two chambers 6 and 6 have changed parts. It will beseen that by this means air is continually drawn from the vessel that isto be exhausted and is discharged into the interior of the casing whenceit is drawn off by means of the auxiliary pump.

In the modification shown in Fig. 3 the channels 13 are cut offimmediately beyond their inner ends. Thereby the action of the apparatusas described above is not altered, the only difference being that theair contained in the chamber that is discharging, is immediately putinto communication with the interior of thecasing, whereas in theconstruction shown in Fig. 2 communication between the dischargingchamber and the interior of the casing is intercepted until thedischarging chamber is filled with liquid.

In Fig. 4 another modification is shown which difiers from theconstruction according to Fig. 2 only in this, that the drum is dividedinto three chambers instead of two. The action is not altered therebyand it will be understood that any desired number of chambers might beemployed. Two chambers however are sufficient and more than three wouldunnecessarily complicate the construc tion of the drum.

I am aware that several vacuum pumps are known the action of whichresembles that of the pump according to my present invention. But in allknown pumps of this kind there is set up a complete circulation of themercury between the vacuum to be produced and the auxiliary vacuumestablished at the outlet of the casing. That is to say the mercuryeither continually enters the drum at a central opening and isdischargedtherefrom at the outer ends of helical channels or vice versa.Thus in these known devices the whole quantity of mercury contained inthe drum is continually brought into contact with the auxiliary vacuumand the final vacuum in turns. Now I have found by experiment that ifthe mercury is exposed for some little time to a less high vacuum suchas the auxiliary vacuum, it will absorb a certain quantity of gas andwhen reintroduced thereupon into the final vacuum which is a highervacuum, it will under the influence of the lower pressure again set freethis absorbed gas. Thus, though with pumps of this kind gas iscontinually being transportedfrom the final vacuum to the auxiliaryvacuum by the normal action of the pump, at the same time 7 ported tothe auxiliary vacuum, evidently the rotation of the pump may becontinued any length of time without further reducing the pressure inthe final vacuum.

The main novel feature by which'my invention differs from these knowndevices is the central intercommunication 14 between the inner chambers6 of the drum. This opening 14 has the effect of considerably increasingthe capacity of the pump and this effect is produced by the fact that inmy pump only that part of the mercury filling the drum which enters thehelical channels 13 is discharged into the casing. The rest passescontinually from one of the inner chambers 6 to the other and viceversa. Therefore only a part of the total quantity of mercury beingequal the interior volume of the helical channels is at all brought intocontact With the auxiliary vacuum and thence returns by the centralopening 9 and the immersed opening 8. It is true that the gas containedin the discharging chamber 6 IOC is forced into the narrow channel 13and is 1 thus to a certain extent compressed and during the beginning ofthe operation it may happen that during this compression the pressure inthe discharging chamber may rise as high as the pressure in theauxiliary vacuum established in the interior of the I casing surroundingthe drum, or even higher.

But this can only take place at the beginning of the operation.

As the exhaustion proceeds the pressure in the final vacuum is latebetween the auxiliary and the final vacuums and the rest willcontinually remain under a pressure only slightly surpassing that of thefinal vacuum. Thus only one tenth or less of the liquid will have anopportunity to absorb gas and to reintroduce it into the final vacuumand consequently the pressure in the final vacuum can with myapparatus'be considerably reduced as compared tothe minimum pressuresobtainable by the known apparatus of this class.

In the modification shown in Fig. 3, it is true, the mercury containedby the discharging chamber is immediately exposed to the pressure of theauxiliary vacuum, but nevertheless also the effect of this drum isconsiderably better than that of any of the known constructions. Thereason is that the fiow of the mercury Within the drum is always awayfrom the exhausting chamber 6 and toward the discharging chamber 6 andtherefore what gas may be absorbed by "the contact of the mercury in thedischarging chamber with gas of a higher pressure, is continuallyprevented from traversing the volume of mercury separatmg the twochambers and thus penetrating into the final vacuum.

Having now particularly described and ascertained the nature of my saidinvention, and in what manner the same is to be performed, I declarethat what I claim is:

1. Means for producing high vacua, comprising a substantiallycylindrical closed casing partly filled with liquid, a drum rotatablymounted in said casing and divided by radial walls into chambers whichcommunicate with each other at the center of said drum by means of anopening between said walls, said chambers also communicating with theinte- 'rior of the casing at the periphery of the drum,

means whereby said drum may be rotated, and means for connecting theinterior of the drum with the vessel to be exhausted.

2. Means for producing high vacua which means consistin the combinationof a substantially cylindrical casing more than half filled with liquidof a drum rotatably mounted therein which drum is divided into innerchambers communicating with each other at the center of the drum andwith the interior of the casing at the periphery, and an outer chamberhaving a central opening communicating with the interior of the casingand other openings placed near the periphery and communicating with theinner chambers, and of means for rotating the drum.

3. Means for producing high vacua'which means consist in the combinationof a substantially cylindrical casing connected to an ordinary air pumpand more than half filled with liquid, of a drum rotatably mountedtherein, said drum being divided into inner chambers communicating witheach other at the center of the drum and with the interior of the casingat the periphery of the drum and an outer chamber having a centralopening below the surface of the liquid and peripheral openingscommunicating with the inner chambers, of helical channels interposedbetween the inner chambers of the drum and the interior of the casingand of a pipe connected to the vessel to be exhausted and passingthrough the central opening into the outer chamber, its end being bentupward therein to a level above the surface of the liquid.

4. Means for producing high vacua which means consist in the combinationwith a substantially cylindrical casing more than half filled withliquid, means for partially exhausting said casing, of a drum rotatablymounted Within said casing and being more than half immersed in saidliquid, said drum being divided by substantially radial partitions intoinner chambers communicating with. each other at a point continuallyimmersed in the liquid and communicating with the interior of the casingby means of helical channels at the periphery of the drum and an outerchamber hermetically connected to the vessel to be exhausted and beingin communication with the inner chambers by means of holes placed nearthe periphery of the drum and of means for rotating the drum.

In testimony that I claim the foregoing as my invention, I have signedmy name in presence of two subscribing witnesses.

WOLFGANG GAEDE.

Witnesses:

WILH ENGLER, ROBERT BENDER.

